TheRadioBoard

Thanks eb!

So even with about twice the wire ac resistance and "loose" stacking - the stacked toroids make an inductor with a decent Q.

Very interesting eb. And again, nice work. Makes us think that's for sure.

73, Dan

Another thought

I acquired an old crystal set that used three separate coils in series. My guess was that the technique may have reduced the interwinding capacitance and maybe allowed a greater tuning range and possibly increased the overall Q ? The three were tapped to a front panel switch so that the user could pick the optimum combination. An old version of the 'contra coil' I imagine.

Has anyone experimented with series coils on ferrite? Something like three different ferrite rods or toroids?

Some of the old ferite slug RF and IF transformers were wound in several sections that looked like honeycomb winding.
More often you see chokes wound in sections labeled PI wound, low capacity, or low loss.
"paddle wheel" coils crop up ocasionally but I've only run across a couple ads. The selling points seem to be compactness and low loss. Low loss as in close in fields, not high Q.

I did that last week with aircoils ("end to end", and "at right angles").
"Q" was less at right angles (where there was no mutual inductance).

Don't think I have tried it with ferrite, except for a group of (5) separated windings on the same bar. Q was disappointingly less than for the same inductance value wound as a single coil. Co (which I was interested in) was also worse than with the single coil (must be a reason?).

Don't have to tell exray this, but I think the big "Q" improver is the mutual inductance factor with close winding. Double the turns on the same former gives four times the inductance value whereas 2 coils with the same turns (not sharing any field), has only twice the inductance. Higher inductance gives higher XL and, up to a point, should give higher Q.
I think you need the turns minimally separated to build up the required field necessary to get the high Q.

As always, just guessing.

...............................................

Hi Dan,the cores are held very tight in the rod structure,I doubt
that a layer of superglue would improve this.It probably helps
that these cores come from the same manufacturing lot,
dated 5/10/01,made in USA.While testing Q's I tried to see how
this coil would perform with fewer cores at 1700kHz.I found the
highest Q with four of the cores stacked centered.
At L=116uH,1700kHz-Q800,1000kHz-Q850,tapering off to
530kHz-Q590,with 600pf aux cap.

Hi Exray,as this is a project to develop a wide range
large aperture ferrite rod,2000kHz to as low as practical,
I will encounter tapped coils for the lowest ranges.
As I have further results I will report these in the antenna forum.
Eb.

eb
Your antenna experiments are of extreme interest to me. I'm working on a Litz loose coupler and using ferrite rods between PVC pipe for the primary coil. Preliminary Q results run parallel to your experiments. A disappointment as I was expecting a lot higher.
A couple things I've noticed on the PVC coil is that the rise and fall times 10% to 90% are sharper and the ground noise level is lower. You may want to look at low signal reception data on the various designs.

Hello homebrew, I reply your email two days ago, do you read it?

_________________
I love crystal radio!

MAK:
Have not received your e-mail. Cannot find it. Please resend.
The icon on my post should be correct.

I have time to do it. please tell me how you want to compare. 15-20 feet of teflon coated wire should be enough. Thanks!

_________________
I love crystal radio!

*
The cheap silver plated teflon wire on Ebay is all 26 ga. Wind it the same inductance as the solid wire coil. That should give a good idea if it is worthwhile using it on sets in place of solid wire or Litz.
What is the source of your syringes? I'm having trouble locating anything close to them. My cost on the wire mailed was 40 cents. Shipping it cost 1.75.

FWIW - I have sourced syringes (some large - inch, inch and 1/4?) at veterinary supply outlets.

I got my syringes from China.

_________________
I love crystal radio!

Hi homebrew,

I compare your 19 strands silver plated teflon coated wire with AWG 22 solid magnet wire and 175/46 litz wire.





All three coils are 240 uH with the same amidon-61 4" by 0.5" ferrite rod.

AWG 22 solid magnet wire, 60 turns, 1.7" width.
550 KHz, 349 pf, 102 Q.
800 KHz, 166 pf, 104 Q.
1700 KHz, 35 pf, 112 Q.

silver plated wire, 62 turns, 2.4" width.
550 KHz, 351 pf, 252 Q
800 KHz, 164 pf, 273 Q.
1700 KHz, 34 pf, 299 Q

175/46 litz, 61 turns, 2.0" width.
550 KHz, 355 pf, 750 Q.
800 KHz, 166 pf, 800 Q.
1700 KHz, 34 pf, 662 Q.

over twice the Q, I would go for it.

Thanks, It looks like a good sub for solid wire at two cents per foot.
Higher Q with a smaller guage wire. I can live with that.
The coil is longer than I expected so the insulation is thick giving a bit of spacing between turns which should raise the Q a little. Can you space the solid wire one a bit to give it a width closer to the 2.0 and 2.4 inches of the other coils?